COVID-19 Vaccine Boosters: Can You Mix and Match?

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healthcare provider administering COVID-19 vaccine to man
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All fully vaccinated adults ages 18 and older are eligible to receive a COVID-19 vaccine booster, according to the Centers for Disease Control and Prevention (CDC). The Food and Drug Administration (FDA) authorized boosters of all three COVID-19 vaccines—Pfizer-BioNTech, Moderna and Johnson & Johnson (J&J).

Even before booster authorization, clinical groups supported the idea of mixing and matching the type of COVID-19 booster with the original vaccine. After reviewing several studies, the FDA and CDC say the mix and match approach is safe.

Learn about the types of COVID-19 vaccine boosters and why mixing and matching the type of COVID-19 booster might be a good idea to protect yourself and those around you from serious illness.

Types of COVID-19 Boosters

Research so far has shown that all three of the vaccines available in the United States are highly effective at preventing serious illness, hospitalization and death in vaccinated people. However, vaccination is not as protective against infection and the spread of the virus to others. Booster doses stimulate immunity and increase protection from COVID-19.

When you can receive a booster depends on the vaccine you received for your primary vaccination:

  • Pfizer-BioNTech COVID-19 vaccine: If this is your primary vaccine, wait at least six months to receive a booster of any of the three vaccines.
  • Moderna COVID-19 vaccine: If this is your primary vaccine, wait at least six months to receive a booster of any of the three vaccines.
  • Johnson & Johnson COVID-19 vaccine: If this is your primary vaccine, wait at least two months to receive a booster of any of the three vaccines.

Safety of COVID-19 Booster Mix and Match

After reviewing the data from research studies and clinical trials of thousands of participants, the FDA and CDC approved the safety of mixing and matching the COVID-19 vaccine booster with the primary vaccine. So, whether you prefer to get a booster of the same vaccine you originally received or a booster of a different type, it’s safe and effective to receive either one.

Getting a different vaccine than your original dose may provide even better protection against COVID-19. A study examining all possible combinations of the Pfizer-BioNTech, Moderna and J&J vaccines and boosters showed, on average, a 20-fold increase in the immune system’s antibody response when the booster dose differed from the primary dose(s). People who received the J&J vaccine for the primary vaccination and a Moderna or Pfizer booster dose saw the biggest increase in antibody response.

In fact, the CDC recommends choosing one of the mRNA vaccines as your booster dose. So, if you received the J&J vaccine, you are advised to get the Pfizer-BioNTech or Moderna booster.

Common Side Effects of COVID-19 Boosters

The most common side effects of booster shots for people in clinical trials include:

The Pfizer-BioNTech and J&J boosters contain a full dose—the same amount of vaccine as the primary vaccine dose.

The Moderna booster dose is half the amount of the primary vaccine dose. This is because, in some instances, the primary dose of the Moderna vaccine increased the risk of myocarditis and pericarditis, which are inflammatory heart conditions. While still uncommon, this inflammatory response was more likely to happen after the second dose of the Moderna vaccine for men under 40, especially in younger men between 18 and 24. To reduce the health risk, the FDA and CDC determined that a half dose of the Moderna booster is safer than a full dose.

Who Needs a COVID-19 Booster 

Booster doses of all types of vaccines are common, particularly in young children as they become fully vaccinated against various diseases. Even in adults, a booster for the DTaP vaccine—which protects against diphtheria, tetanus and pertussis—is recommended every 10 years to prevent serious illness. Researchers liken booster shots to a “reminder” for the immune system to protect the body against any given disease.

Similarly, people at high risk of becoming seriously ill from COVID-19 would benefit from the extra protection of a booster shot, as the immune system “memory” fades. Additionally, since COVID-19 variants continue to emerge, the body may need additional help protecting against this potentially fatal disease.

Populations Eligible for a COVID-19 Booster

The CDC recommends a booster for people in the following at-risk groups, including:

  • People age 65 or older
  • People 18 and older at a high risk of becoming seriously ill 
  • People 18 and older who work or live in high-risk settings, such as the healthcare industry
  • All people 18 and older who received the J&J vaccine

However, the FDA updated the booster authorizations to include all adults, regardless of risk factors. Some states have already begun administering booster doses to the general population. Getting a booster shot is a personal choice. Consider your age, health status, and living or working environment in making the decision.

Booster vs. Third Dose

A booster shot is technically and medically different from a third dose. Also called an additional dose, the third dose is for people who are immunocompromised and may have little protection from the first two doses of the Pfizer-BioNTech or Moderna vaccines or from a single dose of the J&J vaccine.

The additional dose contains the same amount of product as the booster dose (except for the half-dose Moderna booster), but the purpose is different: The additional dose is necessary to build immunity; whereas, the booster is necessary to strengthen existing immunity.

Bottom Line on COVID-19 Boosters 

As with any vaccine, all three COVID-19 vaccine boosters come with some risk of side effects, both mild and serious. However, also like any other vaccine, serious reactions are not common. Talk with your doctor if you need help deciding whether to get a COVID-19 vaccine booster shot. Your doctor can also help you decide whether to get a booster of the same type (match) or mix your COVID-19 booster.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Nov 19
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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